A comparative analysis of North American adolescent and adult mass murderers.

Thirty adult mass murderers and 34 adolescent mass murderers in North America are compared on both offender and offense variables to delineate similarities and differences. Findings indicate a plethora of psychiatric disturbances and odd/reclusive and acting-out personality traits. Predisposing factors include a fascination with weapons and war among many of the adolescents and the development of a "warrior mentality" in most of the adults. Precipitating factors indicate a major rejection or loss in the hours or days preceding the mass murder. Results are interpreted through the lens of threat assessment for targeted violence (Borum, Fein, Vossekuil, & Bergland 1999), recognizing that a fact-based, dynamic behavioral approach is most useful for mitigating risk of such an extremely low-base-rate violent crime. Copyright 2004 John Wiley & Sons, Ltd.